Olap Slicer

[cognos05]

Hi ,

This is purely related to olap reporting .

I wanted to add a slicer like ,

if(caption(#prompt('prmagency','mun','[ABC]')#)='Test1')
Then
([Region1])
Else
([Region2])

I am gettign an error

OP -ERR-0233  Slicer member set expression = if rolevalue ('_member caption')
For anything other than a set of members from the datasource ,the results may not be what you expect.

This caption of prompt works fine on a calculation if not used in slicer.

Just trying to understand what i am trying to do wrong here .